1. Field of the Invention
The present invention relates generally to a mechanism for adjusting the optical axis of a lamp casing for a vehicle and particularly to a mechanism of this type in which the lamp casing is swingingly moved directly by linear movement of an operating wire so that the optical axis of the lamp casing can be accurately and surely adjusted in accordance with the control from a control device without being affected by working and fastening errors produced in the mechanism and so that there is scanty the possibility that the operation of the mechanism is rendered impossible by interposition of a foreign matter.
2. Description of the Prior Art
A conventional mechanism for adjusting the optical axis of, for example, a head lamp of a vehicle is generally constructed and arranged as shown in FIG. 1 of the accompanying drawings and includes a lamp casing 10 swingably supported by a hinge joint 11, a bell crank lever 12 swingably supported at a fulcrum and operatively connected at one arm to the lamp casing 10, an operating rod 13 operatively connected to the other arm of the bell crank lever 12, and a control device 14 operatively connected to the operating rod 13 through an operating wire 15 and a lever 16 for manually or automatically adjusting the angle of irradiation of a lamp in the lamp casing 10. As a result, in the conventional optical axis adjusting mechanism, an operating force effected to the operating rod 13 by the control device 14 is transmitted to the lamp casing 10 by way of the bell crank lever 12 by which linear movement of the operating rod 13 is converted to swinging movement of the bell crank lever 12. Thus, the conventional optical axis adjusting mechanism has had disadvantages that, when errors are produced in the working and fastening of the bell crank lever 12, the angular position of the lamp casing 10 can not be accurately adjusted in accordance with the control from the control device 14, and that the bell crank lever 12 is locked by interposition of a foreign matter to render the operation of the optical axis adjusting mechanism impossible. Furthermore, there has been existent an inconvenience that the provision of the bell crank lever 12 renders the working, fastening and assembling of the optical axis adjusting mechanism difficult and complicates the construction of the mechanism.